Ethanol induces neuroimmune dysregulation and soluble TREM2 generation in a human iPSC neuron, astrocyte, microglia triculture model

Abstract

Alcohol use disorders (AUDs) affect substantial populations worldwide and increase the risk of developing cognitive impairments and alcohol-associated dementia. While chronic inflammatory signaling likely plays an important role in alcohol-associated neurological sequalae, the precise mechanisms underlying alcohol-associated neuropathology remain enigmatic. We hypothesize that alcohol leads to neuroimmune dysregulation among neurons, astrocytes, and microglia; and is perpetuated by innate immune signaling pathways involving cell-cell signaling. To investigate how alcohol dysregulates neuroimmune interactions in a human context, we constructed a triculture model comprising neurons, astrocytes, and microglia derived from human induced pluripotent stem cells. After exposure to ethanol, we observed significant differential gene expression relating to innate immune pathways, inflammation, and microglial activation. Microglial activation was confirmed with morphological analysis and expression of CD68, a lysosomal-associated membrane protein and marker for phagocytic microglial activation. A striking finding in our study was the elevation of TREM2 expression and, specifically, TREM2 alternative splice variants that are predicted to give rise to soluble TREM2. TREM2 has been reported to be a risk factor for Alzheimers disease. These results suggest that ethanol exposure in the brain may lead to increased microglial activation and production of soluble isoform named TREM2219 through alternate splicing. Deciphering the molecular and cellular mechanisms underpinning ethanol-related neuroimmune dysregulation within a human context promises to shed light on the etiology of AUD-related disorders, potentially contributing to the development of effective therapeutic strategies. HighlightsO_LIWe prepared a "triculture" of human iPSC-derived neurons, astrocytes and microglia C_LIO_LIEthanol treatment produces substantial changes in gene expression with prominent effects on neuroimmune signaling C_LIO_LISeveral microglia-specific genes are induced by ethanol in tricultures but not in cultures of microglia alone C_LIO_LITREM2 expression is increased following ethanol treatment and results indicate a differential splicing of isoforms, encoding a soluble form of TREM2 C_LI